This is a phase-II prospective, randomized, open-labelled, dose-ranging study to evaluate the safety and efficacy of intermittently administered intravenous foscarnet for salvage therapy of active CMV retinitis in AIDS patients. All patients will receive a standard course of Foscarnet induction therapy and will be randomized to receive one of two maintenance regimes. These patients are either intolerant of ganciclovir on the basis of myelosuppression or are unresponsive to an adequate course of ganciclovir therapy.